This invention relates in general to systems for transmitting video signals, and in particular, a system for updating channel lineup for broadcasting and switched digital broadcasting services.
Television program are delivered through coaxial cables to subscribers, where the capacity is limited by the bandwidth of the coaxial cables. With the introduction of high definition television programs, and increased number of channels that are offered to cable subscribers, there is a need for increasing the efficiency in bandwidth use of coaxial cables in digital video transmission. This is especially the case since a large portion of the capacity is devoted to analog transmission through the cables.
One solution for a more efficient use of the capacity available in coaxial cables is known as the switched broadcasting architecture. Television programs are traditionally broadcast to all subscribers whether or not the subscribers are watching the programs. A large percentage of television programs delivered in this manner are actually not watched by subscribers. In a switched broadcasting architecture, television programs are delivered only to subscribers who request such programs. While the specific frequency and program for a switched broadcast program may vary in time, the channel number as seen by the subscriber will always remain the same. In this manner, the subscriber will not notice any difference between the two different approaches. For more detailed explanation of the switched broadcasting architecture, please see the article “The Statistics of Switched Broadcast,” by Nishith Sinha, from BigBand Networks at www.bigbandnet.com.
Switched broadcasting may be operated in two different modes. In the first switched mode known as the switched multicast, more than one subscriber within the network node, or service group, may access the same program stream. This provides additional bandwidth savings. Thus if a subscriber wants to watch a program that is currently being delivered to other subscribers within the same node or service group, the new viewer simply joins the existing switched session. Consequently, no additional capacity is consumed by the incremental subscriber.
Alternatively, in a mode known as switched unicast, each subscriber may receive a unique program stream. For further details concerning the two types of switched broadcast modes, please see “Evolving Switched Broadcast Beyond First Generation Developments,” by Jim Nguyen and Ran Oz of Bigband Networks at www.bigbandnet.com.
With the adoption of the switched broadcast modes, it is desirable to provide a technique for utilizing the traditional broadcasting tier and the switched broadcasting tier in a manner that allows bandwidth utilization efficiency to be improved.
Considerations similar to those above may be applicable to other systems for delivering video programs, such as to cellular telephone systems. It is therefore desirable to provide an improved technique for bandwidth utilization in systems such as cellular telephone systems.